Hide content overflow on the document page

Summary:
A number of ways to do this. For now we'll just hide any content that overflows.
Could scroll it instead. Also allow long links to break inside words so that the
full link is visible, don't love doing it, but it will be fine for now.

Test Plan:
- Resize your viewport to something very small on a document
- There should not be a horizontal scrollbar

Differential Revision: https://phabricator.opengovfoundation.org/D168

Author: doshitan

resources/assets/sass/document.scss

@@ -225,6 +225,7 @@ blockquote {
   color: white;
   padding: $jumbotron-padding * 2 $jumbotron-padding;
   font-size: $jumbotron-font-size * 0.8;
+  overflow: hidden;
 
   a {
     @extend .alt-link;
@@ -287,6 +288,7 @@ blockquote {
   .document-title {
     margin-top: $jumbotron-padding * 2;
     font-size: 2em;
+    overflow: hidden;
   }
 
   @media screen and (min-width: $screen-sm-min) {
@@ -355,20 +357,27 @@ blockquote {
   }
 
   #page_content {
+    overflow: hidden;
+
     h1, h2, h3, h4, h5, h6 {
       font-family: $font-family-serif;
 
       &:first-child {
         margin-top: 0;
       }
     }
+
+    a {
+      word-wrap: break-word;
+    }
   }
 }
 
 #comments {
   background-color: $ogf-blue-white;
   padding-top: $line-height-computed;
   padding-bottom: $line-height-computed;
+  overflow: hidden;
 
   #all-comments-count {
     @extend .h1;